Folic Acid Confers Tolerance against Salt Stress-Induced Oxidative Damages in Snap Beans through Regulation Growth, Metabolites, Antioxidant Machinery and Gene Expression

Abstract

Although the effect of folic acid (FA) and its derivatives (folates) have been extensively studied in humans and animals, their effects are still unclear in most plant species, specifically under various abiotic stress conditions. Here, the impact of FA as a foliar application at 0, 0.1, and 0.2 mM was studied on snap bean seedlings grown under non-saline and salinity stress (50 mM NaCl) conditions. The results indicated that under salinity stress, FA-treated plants revealed a significant (p ≤ 0.05) increase in growth parameters (fresh and dry weight of shoot and root). A similar trend was observed in chlorophyll (Chl b), total chlorophyll, carotenoids, leaf relative water content (RWC), proline, free amino acids (FAA), soluble sugars, cell membrane stability index (CMSI), and K, Ca, and K/Na ratio compared to the untreated plants. In contrast, a significant decrease was observed in Na and salinity-induced oxidative damage as indicated by reduced H2O2 production (using biochemical and histochemical detection methods) and rate of lipid peroxidation (malondialdehyde; MDA). This enhancement was correlated by increasing the activities of antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (G-POX), and ascorbate peroxidase (APX). Gene expression analyses conducted using qRT-PCR demonstrated that genes coding for the Na+/H+ antiporter protein Salt Overly Sensitive 1 (SOS1), the tonoplast-localized Na+/H+ antiporter protein (NHX1), and the multifunctional osmotic protective protein (Osmotin) were significantly up-regulated in the FA-treated plants under both saline and non-saline treatments. Generally, treatment with 0.2 mM FA was more potent than 0.1 mM and can be recommended to improve snap bean tolerance to salinity stress.

Folic Acid Reinforces Maize Tolerance to Sodic-Alkaline Stress through Modulation of Growth, Biochemical and Molecular Mechanisms

“…In this study, plants exposed to sodic-alkaline stress displayed a significant inhibition in plant growth as indicated by reduced shoot and root fresh weights compared to those in unstressed conditions. Generally, salinity can seriously restrict plant growth and development in many plant species due to the ionic toxicity and osmotic stress [8,50,51]. Moreover salt stress suppresses the rate of cell division [52], homeostasis of phytohormones [53], capacity of photosynthesis [54], and uptake of nutrients [2,55].…”

“…The cell-membrane stability index was estimated as described by Abd Elbar, et al [35]. Some leaf discs (8) were incubated for 24 h in 10 mL deionized water on a shaker. Then EC 1 values of contents were measured by EC meters.…”

“…Furthermore, sodic-alkaline stress has harmful impacts on the cell-membrane stability index, plant-water relations, photosynthetic pigments, and a wide array of physiological, biochemical, and molecular aspects [5][6][7]. When plants are grown under saline or alkaline conditions, they are subjected to three major problems: (i) water deficiency through osmotic stress and the hindering water uptake, (ii) disturbance of the plant nutritional status through affecting ion-transport systems, and (iii) sodium toxicity by increasing its uptake in the susceptible tissues [2,[6][7][8][9][10]. Exposing plants to saline and/or alkaline stress can affect the concentration of osmolytes (sugars, amino acids, polyamines, etc.)…”

“…These effects can be explained by the folates' ability to stimulate many precursors and intermediate pathways such as the biosynthesis of porphyrins, S-adenosylmethionine (SAM), and isoprenoids [15,20]. On the other hand, exogenous folic acid has demonstrated strong antioxidant properties that are responsible for reducing the oxidative damage in several plant species under various abiotic stresses, i.e., drought [20,21], salinity [8,22,23], and heavy metals [24]. Generally, when abiotic-stressed plants are treated with a strong antioxidant, other toxic molecule such as methylglyoxal (MG) can be diminished [25].…”

Improving the Tolerance to Salinity Stress in Lettuce Plants (Lactuca sativa L.) Using Exogenous Application of Salicylic Acid, Yeast, and Zeolite

“…Plants growing under saline conditions have been reported to be affected in three ways: reduced water potential in the rhizosphere causing water shortage, phytotoxicity of ions such as Na + and Cl − , and imbalance of nutrients reducing their absorption and transport in plants [ 6 ]. Consequently, salinity influences all of the main processes, such as growth, photosynthesis, and metabolism reactions [ 7 ].…”